Detection of a pair density wave state in UTe2

• Published in: Nature (London) Vol. 618; no. 7967; pp. 921 - 927
• Main Authors: Gu, Qiangqiang, Carroll, Joseph P., Wang, Shuqiu, Ran, Sheng, Broyles, Christopher, Siddiquee, Hasan, Butch, Nicholas P., Saha, Shanta R., Paglione, Johnpierre, Davis, J. C. Séamus, Liu, Xiaolong
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29-06-2023; Nature Publishing Group
• Subjects: 639/766/119/1003; 639/766/119/2792; 639/766/119/995; Data processing; Density; Electron states; Electronic properties; Electrons; Energy; Energy gap; Energy resolution; Fermions; Fourier transforms; Humanities and Social Sciences; Information processing; Magnetic fields; Microscopy; multidisciplinary; Order parameters; Quantum phenomena; Scanning tunneling microscopy; Science; Science & Technology - Other Topics; Science (multidisciplinary); Superconductors; Symmetry; Topography; Topological superconductors; Visualization
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-023-05919-7

Spin-triplet topological superconductors should exhibit many unprecedented electronic properties, including fractionalized electronic states relevant to quantum information processing. Although UTe
2
may embody such bulk topological superconductivity
1
–
11
, its superconductive order parameter Δ(
k
) remains unknown
12
. Many diverse forms for Δ(
k
) are physically possible
12
in such heavy fermion materials
13
. Moreover, intertwined
14
,
15
density waves of spin (SDW), charge (CDW) and pair (PDW) may interpose, with the latter exhibiting spatially modulating
14
,
15
superconductive order parameter Δ(
r
), electron-pair density
16
–
19
and pairing energy gap
17
,
20
–
23
. Hence, the newly discovered CDW state
24
in UTe
2
motivates the prospect that a PDW state may exist in this material
24
,
25
. To search for it, we visualize the pairing energy gap with μeV-scale energy resolution using superconductive scanning tunnelling microscopy (STM) tips
26
–
31
. We detect three PDWs, each with peak-to-peak gap modulations of around 10 μeV and at incommensurate wavevectors
P
i
=1,2,3
that are indistinguishable from the wavevectors
Q
i
=1,2,3
of the prevenient
24
CDW. Concurrent visualization of the UTe
2
superconductive PDWs and the non-superconductive CDWs shows that every
P
i
:
Q
i
pair exhibits a relative spatial phase
δϕ
 ≈ π. From these observations, and given UTe
2
as a spin-triplet superconductor
12
, this PDW state should be a spin-triplet PDW
24
,
25
. Although such states do exist
32
in superfluid
3
He, for superconductors, they are unprecedented.
A spin-triplet pair density wave is discovered in the candidate topological superconductor UTe
2
using superconductive scanning tunnelling microscopy tips.